linux-kernel - Re: [net-next RFC V3 PATCH 4/6] tuntap: multiqueue support

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Message-ID: <20120625084151.GA18987@redhat.com>
Date:	Mon, 25 Jun 2012 11:41:51 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	habanero@...ux.vnet.ibm.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, krkumar2@...ibm.com,
	tahm@...ux.vnet.ibm.com, akong@...hat.com, davem@...emloft.net,
	shemminger@...tta.com, mashirle@...ibm.com
Subject: Re: [net-next RFC V3 PATCH 4/6] tuntap: multiqueue support

On Mon, Jun 25, 2012 at 11:25:53AM +0300, Michael S. Tsirkin wrote:
> On Mon, Jun 25, 2012 at 02:10:18PM +0800, Jason Wang wrote:
> > This patch adds multiqueue support for tap device. This is done by abstracting
> > each queue as a file/socket and allowing multiple sockets to be attached to the
> > tuntap device (an array of tun_file were stored in the tun_struct). Userspace
> > could write and read from those files to do the parallel packet
> > sending/receiving.
> > 
> > Unlike the previous single queue implementation, the socket and device were
> > loosely coupled, each of them were allowed to go away first. In order to let the
> > tx path lockless, netif_tx_loch_bh() is replaced by RCU/NETIF_F_LLTX to
> > synchronize between data path and system call.
> 
> Don't use LLTX/RCU. It's not worth it.

Or maybe we should use LLTX. Need to think about it.
But if yes I'd like a separate patch moving tun to LLTX
and move it always to LLTX. Don't play with LLTX at runtime.

-- 
MST
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